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JP2010057052

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DESCRIPTION JP2010057052
The present invention provides a microphone unit in which acoustic characteristics are not
deteriorated even when a vibrating film is disposed at a position deviated from an opening of a
housing and a side wall portion and a housing are close to or in contact with each other. A
microphone unit (110A) includes a housing (611) including a first space inside. The housing 113
includes a housing opening 611A that communicates the first space with the outside. The
microphone unit 110A is disposed in the first space, the oscillation film 113 disposed in the first
space, an electric circuit unit 240 that outputs an electric signal based on the vibration of the
oscillation film 113, and the oscillation film 113. And sidewall portions 112A thicker than the
above. The side wall portion 112 </ b> A supports the periphery of the vibrating membrane 113
to shift the vibrating membrane 113 from below the case opening 611 </ b> A. The side wall
portion 112A includes a side wall opening 112B communicating the second space above the
vibrating membrane 113 with the outside. [Selected figure] Figure 2
マイクロホンユニット
[0001]
The present invention relates to a microphone unit, and more particularly to a microphone unit
in which a vibrating membrane is disposed offset with respect to an opening of a housing
constituting the microphone unit.
[0002]
There is known a microphone unit that receives voice from the outside and converts the voice
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into an electrical signal.
Such a microphone unit is preferably small (thin) because it is used, for example, as an audio
input device of a mobile phone or other mobile terminal. In particular, in recent years, with the
reduction in thickness of mobile phones and the like, the demand for the size required for each
component has also become severe. For example, as a microphone unit, a thickness of 1.5 mm or
less is required. Therefore, techniques for reducing the size (thinning) of the microphone unit
have been proposed.
[0003]
For example, in Japanese Patent Application Laid-Open No. 2001-54196 (Patent Document 1), a
fixed electrode and a vibrating membrane are disposed at a constant interval, and an audio signal
given to the vibrating membrane is detected by a change in electrostatic capacitance
therebetween An electret condenser microphone is disclosed. According to Japanese Patent
Application Laid-Open No. 2001-54196 (Patent Document 1), in the electret condenser
microphone, the fixed electrode, the vibrating film, and the semiconductor element are
accommodated in parallel in a box-shaped case made of an insulating material.
[0004]
Moreover, the card-type MEMS microphone is disclosed by Unexamined-Japanese-Patent No.
2007-306125 (patent document 2). According to Japanese Patent Laid-Open No. 2007-306125
(Patent Document 2), a card-type MEMS microphone is formed by a substrate having a first
through hole and a second through hole, a diaphragm electrode, and a back air chamber. A
MEMS chip mounted at a position surrounding the outlet of the first through hole and converting
a sound signal propagated to the diaphragm electrode into an electric signal, and a substrate
surface opposite to the side on which the MEMS chip is mounted And an acoustic resistance
material mounted at a position covering the first through hole. The substrate has a terminal for
transmitting an electrical signal output from the MEMS chip to the electronic device, and has a
card shape that can be attached to and detached from the electronic device. The second through
hole is a through hole through which the sound signal is diffracted and propagated to the
diaphragm electrode.
[0005]
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Moreover, the microphone is disclosed by Unexamined-Japanese-Patent No. 2007-124449
(patent document 3). According to Japanese Patent Laid-Open No. 2007-124449 (Patent
Document 3), a conductive electrode and a movable diaphragm electrode disposed opposite to
each other with a gap forming a part of a first sound pressure passage between the conductive
electrode and the conductive electrode Is formed as a so-called MEMS composed of a mechanical
component and an electrical component formed on the semiconductor substrate. By applying a
voltage between the conductive electrode and the movable diaphragm electrode to generate
electrostatic attraction and adsorb the movable diaphragm electrode to the conductive electrode,
the first sound pressure passage is opened or closed.
[0006]
Moreover, the semiconductor electret condenser microphone is disclosed by UnexaminedJapanese-Patent No. 2000-165999 (patent document 4). According to Japanese Patent LaidOpen No. 2000-165999 (Patent Document 4), a microphone comprises a semiconductor chip on
which necessary electronic circuits are formed, an electrode layer laminated on the surface of the
semiconductor chip through an insulating layer, and the electrode An insulating film formed on
the layer, a vibrating film adhered to the insulating ring, and a predetermined space between the
vibrating film and the insulating film, interposed between the ring and the insulating film And a
spacer layer. The vibrating membrane is one obtained by electretizing a polymer FEP film having
an electrode layer formed on one side.
[0007]
Moreover, the condenser microphone is disclosed by Unexamined-Japanese-Patent No. 200614267 (patent document 5). According to Japanese Patent Laid-Open No. 2006-14267 (Patent
Document 5), a support located on the upper stage of the fixed electrode, which insulates the
fixed electrode and the metal case, is located between the uppermost stage and the support in
the metal case. And an FET electrically connected to the metal case and the support, for
amplifying and converting a potential change due to a change in electrostatic capacitance
between the vibrating membrane and the fixed electrode due to the vibration of the vibrating
membrane into an electrical signal. A plurality of acoustic wave inlets are perforated, the
transmission of the acoustic waves flowing into the acoustic wave inlets of the printed circuit
board is delayed, and the fixed electrode is formed on the gate of the FET formed on the printed
circuit board Electrically connect. JP-A-2001-54196 JP-A-2007-306125 JP-A-2007-124449 JP-
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A-2000-165999 JP-A-2006-14267
[0008]
In the above-mentioned microphone unit, the thickness of the vibrating film itself for detecting
the sound wave is about several μm. However, the side wall supporting the diaphragm has a
thickness of about 400 μm, and the ratio of the size (thickness) of the side wall to the size
(thickness) of the entire microphone unit is large. Further, in the microphone unit, it is preferable
not to dispose the diaphragm immediately below the opening in order to prevent malfunction
caused by dust coming in from the opening to which sound is input and adhering to the
diaphragm. That is, it is preferable that the vibrating film does not overlap immediately below the
opening. In other words, it is preferable that the vibrating membrane and the side wall be
arranged so that the vibrating membrane can not be seen from the outside of the microphone
unit through the opening. For this reason, the microphone unit is configured such that the sound
input from the opening portion passes the side wall portion and reaches the diaphragm.
[0009]
However, when the thickness of the entire microphone unit is reduced, the inner wall surface of
the housing constituting the microphone unit and the side wall portion supporting the vibrating
film come close to or abut on each other, and the sound path path becomes narrow. Since the
acoustic impedance is increased by the reduction of the cross-sectional area of the sound path,
the acoustic characteristics of the microphone unit are degraded. For example, there is a problem
that a flat high frequency characteristic can not be obtained because the resonance frequency of
the space determined from the internal space in the microphone unit is lowered.
[0010]
The present invention has been made to solve the above-mentioned problems, and the main
object of the present invention is to place the vibrating film at a position shifted from the
opening of the housing, and the side wall portion and the housing are close to each other.
Alternatively, it is to provide a microphone unit in which the acoustic characteristics do not
deteriorate even if they are in contact.
[0011]
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In order to solve the above problems, according to one aspect of the present invention, a
microphone unit is provided.
The microphone unit includes a housing including a first space therein. The housing includes a
housing opening communicating the first space with the outside. The microphone unit includes a
vibrating membrane disposed in the first space, an electric circuit unit that outputs an electrical
signal based on the vibration of the vibrating membrane, and a sidewall portion disposed in the
first space and thicker than the vibrating membrane. And further comprising The side wall
portion displaces the vibrating membrane from below the case opening by supporting the
periphery of the vibrating membrane. The side wall portion includes a side wall opening
communicating the second space above the vibrating membrane with the outside.
[0012]
Preferably, the side wall opening is located on the side of the housing opening of the side wall.
Preferably, the sidewall opening includes a notch formed by forming at least a portion of the
sidewall portion lower than the other portions.
[0013]
Preferably, the side wall includes four side walls. The notch is formed by forming the height of a
portion of either side wall lower than the other portion of the side wall.
[0014]
Preferably, the side wall opening includes a hole formed in the side wall. Preferably, the housing
includes an inner wall that constitutes a ceiling of the first space. At least a portion of the
sidewall abuts the inner wall surface.
[0015]
As described above, according to the present invention, the microphone unit does not deteriorate
the acoustic characteristics even if the diaphragm is disposed at a position shifted from the
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opening of the housing and the side wall portion and the housing approach or contact with each
other. Provided.
[0016]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
In the following description, the same components are denoted by the same reference numerals.
Their names and functions are also the same. Therefore, detailed description about them will not
be repeated.
[0017]
First Embodiment <Entire Configuration of Audio Signal Transmitting / Receiving Device 100A>
FIG. 1 is a block diagram showing an overall configuration of an audio signal transmitting /
receiving device 100A according to the present embodiment. Audio signal transmitting /
receiving apparatus 100A according to the present embodiment is, for example, a mobile phone.
As shown in FIG. 1, the audio signal transmitting / receiving apparatus 100A includes a
microphone unit 110A, an amplifying unit 120, an adding unit 130, a speaker 140, and a
transmitting / receiving unit 170. Each of the blocks constituting audio signal transmitting /
receiving apparatus 100A according to the present embodiment is realized by, for example, a
gain adjustment apparatus, an adder, or a dedicated hardware circuit such as a wireless
communication apparatus.
[0018]
However, the audio signal transmission / reception device 100A may be a mobile phone or
personal computer having a CPU (Central Processing Unit) and a storage device, and each block
may be realized as part of the function of the CPU. . That is, a control program for realizing the
following functions may be stored in the storage device, and the function of each block may be
realized by the CPU reading and executing the control program from the storage device.
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[0019]
In FIG. 1, the amplification unit 120 is realized by an amplification circuit using an operational
amplifier or the like, and is connected to the microphone unit 110A, the addition unit 130, and
the transmission / reception unit 170. The amplification unit 120 amplifies the transmission
voice signal input from the microphone unit 110A and outputs the signal to the transmission /
reception unit 170 and the addition unit 130.
[0020]
The transmission / reception unit 170 is realized by a wireless communication device such as an
antenna (not shown), and is connected to the amplification unit 120 and the addition unit 130.
The transmission / reception unit 170 receives a reception voice signal and transmits a
transmission voice signal. More specifically, transmission / reception unit 170 transmits the
transmission voice signal input from amplification unit 120 to the outside, receives a reception
voice signal from the outside, and outputs the reception voice signal to addition unit 130.
[0021]
The addition unit 130 is connected to the transmission / reception unit 170, the amplification
unit 120 and the speaker 140. The addition unit 130 adds the reception voice signal input from
the transmission and reception unit 170 and the transmission voice signal input from the
amplification unit 120 to generate an addition signal, and outputs the addition signal to the
speaker 140.
[0022]
The speaker 140 converts the addition signal input from the addition unit 130 into a reception
voice and outputs it.
[0023]
<Configuration of Microphone Unit 110A> Next, the configuration of the microphone unit 110A
according to the present embodiment will be described.
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FIG. 2 is a front sectional view showing a microphone unit 110A according to the present
embodiment.
[0024]
As shown in FIG. 2, the microphone unit 110 </ b> A includes a microphone substrate 621 and
an upper housing 611 stacked on the microphone substrate 621.
[0025]
The vibrating film 113 and an application specific integrated circuit (ASIC) 240 are disposed on
the top surface of the microphone substrate 621.
The ASIC 240 performs processing such as amplifying a signal based on the vibration of the
vibrating membrane 113. The ASIC 240 is preferably disposed near the vibrating membrane
113. When the signal based on the vibration of the vibrating membrane 113 is weak, the
influence of external electromagnetic noise can be minimized, and the SNR (Signal to Noise Ratio)
can be improved. Further, the ASIC 240 may be configured to incorporate not only an
amplification circuit but also an AD converter or the like so as to perform digital output.
[0026]
The upper housing 611 forms a first space for surrounding (accommodating) the side wall
portion 112A, the vibrating membrane 113, and the ASIC 240 with the microphone substrate
621. At one end of the upper housing 611, a housing opening 611A for transmitting a sound
wave (sound vibration) from the outside of the microphone unit 110A to the first space is
formed. The sound wave reaches the upper surface of the vibrating membrane 113 by passing
through the housing opening 611A and passing through the first space.
[0027]
The ASIC 240 is disposed on the side of the diaphragm 113 opposite to the casing opening 611A
so as not to block the sound wave transmitted from the casing opening 611A to the diaphragm
113. Is preferred.
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[0028]
The vibrating membrane 113 is supported by the side wall portion 112A disposed on the
microphone substrate 621.
The vibrating membrane 113 and the side wall portion 112A supporting the vibrating membrane
113 will be described below. FIG. 3 (A) is a perspective view of the side wall 112A according to
the present embodiment, and FIG. 3 (B) is a plan view of the side wall 112A according to the
present embodiment. FIG. 4 is a front sectional view showing the vibrating membrane 113 and
the side wall portion 112A.
[0029]
As shown in FIGS. 1 to 4, the vibration film 113, the side wall 112A, and the ASIC 240 constitute
a vibration detection unit 111.
[0030]
Referring to FIGS. 2 to 4, the case opening 611A is formed at one end of the upper case 611 of
the microphone unit 110A.
The side wall portion 112A supports the periphery of the vibrating membrane 113, thereby
disposing the vibrating membrane 113 at a position shifted from below the case opening 611A.
As described above, since the vibrating membrane 113 is disposed offset from below the case
opening 611A, the vibrating membrane 113 is not directly exposed to the outside of the
microphone unit 110A. As a result, it is possible to prevent the dust such as dust and dirt from
adhering to the vibrating membrane 113.
[0031]
The outer peripheral surface of the side wall portion 112A according to the present embodiment
is formed of four planes. However, the side wall portion 112A may be configured of four side
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walls. The side wall portion 112A has an opening formed on the side of the case opening 611A.
More specifically, in the side wall portion 112A according to the present embodiment, a part of
the side wall on the side of the casing opening 611A is formed to be lower than the height of the
other side wall. In other words, the side wall portion 112A is formed with the notch portion 112B
on the side of the case opening 611A.
[0032]
From the viewpoint of securing the cross-sectional area of the sound path, and from the
viewpoint of downsizing of the microphone unit 110A, the size of one side (width) of the notch
112B is 0.2 mm or more, and the diameter of the diaphragm 113 (0.5 to It is preferable that it is
1 mm or less. Alternatively, the height of the notch 112B is preferably 0.2 to 0.3 mm.
[0033]
Thus, in the side wall portion 112A according to the present embodiment, the notch 112B is
formed on the side of the case opening 611A, so the side wall 112A is surrounded by the notch
112B and the inner wall surface of the upper case 611. The sound wave can easily reach the
vibrating membrane 113 through the space of the gap. Here, the inner wall surface of the upper
housing 611 constitutes a ceiling of the first space.
[0034]
As shown in FIG. 4, since the side wall of the normal side wall portion is sealed, the sound wave
propagates from above the vibrating membrane 113 to the vibrating membrane 113 beyond the
side wall portion 112A. That is, in the normal side wall portion, the sound pressure Pf is
transmitted from the direction of arrow X in FIG. 4 to the vibrating membrane 113. However, in
the side wall portion 112A according to the present embodiment, the side wall portion 112A and
the inner wall surface of the upper housing 611 are in contact with or close to each other, and
the notch portion 112B is formed on the housing opening 611A side. Because of this, the sound
pressure Pf is transmitted from the arrow direction Y in FIG. 4 to a space (second space) above
the vibrating film 113 surrounded by the side wall portion 112A.
[0035]
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As a result, as shown in FIG. 2, even if the side wall portion 112A is brought into contact with the
inner wall surface (the ceiling of the first and second spaces) of the upper housing 611, the
sound wave can be propagated to the vibrating membrane 113 become. That is, the side wall
portion 112A according to the present embodiment can propagate the sound wave to the
diaphragm 113 while raising the strength of the microphone unit 110A by contacting the
microphone substrate 621 and the inner wall surface of the upper housing 611. It is possible.
[0036]
That is, the microphone unit 110A according to the present embodiment reduces the strength of
the microphone unit 110A by reducing the height of at least a part of the side wall 112A in the
direction of the housing opening 611A with respect to the vibrating membrane 113. It is possible
to secure the cross-sectional area of the sound path from the case opening 611A to the vibrating
film 113 without causing the problem, and it is possible to achieve both thinning of the
microphone unit 110A and good acoustic characteristics.
[0037]
Furthermore, in the microphone unit 110A according to the present embodiment, by shortening
the sound path length, the internal space volume of the housing can be reduced, whereby the
resonance frequency can be kept high.
Then, the volume of the microphone unit 110A can be reduced. Further, the notch 112B of the
side wall 112A can be easily formed, for example, by etching or the like.
[0038]
<Modification of Side Wall> FIG. 5 is a front sectional view showing a modification of the side
wall according to the present embodiment. As shown in FIG. 5, in the side wall portion 112C
according to this modification, a hole portion 112D is formed on the side of the housing opening
portion 611A of the side wall portion 112C. As described above, in the microphone unit 110A
according to the present modification, sound waves from the outside propagate through the
space surrounded by the case opening 611A to the first space. Then, the sound wave propagated
to the first space propagates to the vibrating membrane 113 through the space surrounded by
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the hole 112D.
[0039]
From the viewpoint of securing the cross-sectional area of the sound path and the viewpoint of
downsizing of the microphone unit 110A, the size (or diameter) of one side of the hole 112D is
0.2 mm or more, preferably 0.2 to 0.3 mm. Is preferred.
[0040]
As described above, the hole 112D is formed on the side of the case opening 611A in the side
wall 112C according to the present modification, so the sound wave passes through the space
surrounded by the hole 112D to the diaphragm 113. It can be reached.
That is, in the side wall portion 112C according to the present modification, since the hole
portion 112D is formed on the side of the housing opening 611A, the upper side of the vibrating
film 113 surrounded by the side wall portion 112C from the arrow direction Y in FIG. The sound
pressure Pf is transmitted to the space (second space).
[0041]
By this, as shown in FIG. 5, even if the upper surface of the side wall portion 112C is brought into
contact with or close to the inner wall surface (the ceiling of the first and second spaces) of the
upper housing 611, the sound wave is propagated to the vibrating film 113 It will be possible to
That is, the side wall portion 112C according to the present embodiment can propagate the
sound wave to the diaphragm 113 while raising the strength of the microphone unit 110A by
contacting the microphone substrate 621 and the inner wall surface of the upper housing 611. It
is possible.
[0042]
The side wall 112C according to the present modification can easily form a side wall opening by
forming the hole 112D in the side wall 112C.
[0043]
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Second Embodiment Next, a second embodiment of the present invention will be described.
The audio signal transmitting / receiving apparatus 100B according to the present embodiment
has a differential microphone unit 110B.
[0044]
FIG. 6 is a block diagram showing the entire configuration of the audio signal transmitting /
receiving apparatus 100B according to the present embodiment. Audio signal transmitting /
receiving apparatus 100B according to the present embodiment is, for example, a mobile phone.
As shown in FIG. 6, the audio signal transmitting / receiving apparatus 100B includes a
differential microphone unit 110B, an amplifying unit 120, an adding unit 130, a speaker 140,
and a transmitting / receiving unit 170. The configuration of audio signal transmitting /
receiving apparatus 100B is similar to that of the above-described first embodiment, and
therefore detailed description will not be repeated.
[0045]
<Configuration of Differential Microphone Unit 110B> Hereinafter, a differential microphone unit
110B according to the present embodiment will be described. FIG. 7 is a front sectional view
showing the vicinity of the vibration detection unit 111. As shown in FIG.
[0046]
As shown in FIGS. 6 and 7, the differential microphone unit 110 </ b> B according to the present
embodiment includes a vibration detection unit 111. The differential microphone unit 110B
according to the present embodiment removes background noise by acquiring an acoustic
difference.
[0047]
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The vibration detection unit 111 includes the vibration film 113, the side wall portion 112A, and
an ASIC described later. The vibration detection unit 111 vibrates by sound pressure (amplitude
of sound wave) Pf and Pb from two directions reaching the vibrating membrane 113, and
generates an electric signal according to the vibration. That is, the differential microphone unit
110B receives the transmission voice transmitted from the two directions and converts it into an
electrical signal.
[0048]
In the differential microphone unit 110B according to the present embodiment, the diaphragm
113 receives the sound pressure Pf and Pb from both upper and lower sides, and the diaphragm
113 vibrates according to the sound pressure difference (Pf−Pb). Therefore, when sound
pressure of the same magnitude is simultaneously applied to both sides of the vibrating
membrane 113, the two sound pressures are canceled by the vibrating membrane 113, and the
vibrating membrane 113 does not vibrate. Conversely, when there is a difference in the sound
pressure received on both sides, the vibrating membrane 113 vibrates due to the sound pressure
difference.
[0049]
The configuration of the vibration detection unit 111 including the side wall portion 112A, the
vibration film 113, and the ASIC 240 is the same as that in the first embodiment, and thus the
detailed description will not be repeated here.
[0050]
That is, also in the differential microphone unit 110B according to the present embodiment, the
side wall 112A and the inner wall surface of the upper housing 612 are in contact with or close
to each other, and the notch 112B is formed on the housing opening 612A side. Because of this,
the sound pressure Pf is transmitted from the arrow direction Y in FIG. 7 to the space (second
space) above the vibrating film 113 surrounded by the side wall portion 112A.
Alternatively, as shown in FIG. 5, since the hole 112D is formed on the side of the housing
opening 612A of the side wall 112C, the upper side of the vibrating film 113 surrounded by the
side wall 112A from the arrow direction Y in FIG. The sound pressure Pf is transmitted to the
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space (second space).
[0051]
However, in the differential microphone unit 110B according to the present embodiment, the
sound pressure Pb is transmitted from the direction of arrow Z in FIG. 7 to the space (second
space) below the diaphragm 113 surrounded by the side wall portion 112A. Come.
[0052]
Next, the noise removal principle of the differential microphone unit 110B will be described.
FIG. 8 is a graph showing the relationship between the sound pressure P and the distance R from
the sound source. As shown in FIG. 8, the sound wave attenuates as it travels through a medium
such as air, and the sound pressure (the strength and amplitude of the sound wave) is reduced.
The sound pressure P is inversely proportional to the distance from the sound source, so the
sound pressure P can be expressed as P = k / R (1) in relation to the distance R from the sound
source. In equation (1), k is a proportional constant.
[0053]
Then, as is clear from FIG. 8 and the equation (1), the sound pressure (amplitude of the sound
wave) is sharply attenuated at a position close to the sound source (left side of the graph) and is
gently attenuated as it gets away from the sound source. That is, the sound pressure transmitted
to two positions (d0 and d1, d2 and d3) at which the distance from the sound source differs by
Δd is largely attenuated from d0 to d1 where the distance from the sound source is small (P0P1) There is not much attenuation from d2 to d3 where the distance from the sound source is
large (P2-P3).
[0054]
When the differential microphone unit 110B according to the present embodiment is applied to
the audio signal transmitting / receiving apparatus 100B represented by a mobile phone, the
speech from the speaker is generated from the vicinity of the differential microphone unit 110B.
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Therefore, the sound pressure of the speaker's uttered voice is greatly attenuated between the
sound pressure Pf reaching the upper surface of the diaphragm 113 and the sound pressure Pb
reaching the lower surface of the diaphragm 113. That is, the difference between the sound
pressure Pf reaching the upper surface of the vibrating membrane 113 and the sound pressure
Pb reaching the lower surface of the vibrating membrane 113 is large in the speech voice from
the approaching speaker.
[0055]
On the other hand, distant background noise exists at a position far from the sound source from
the differential microphone unit 110B as compared to the speech of the speaker. Therefore, the
sound pressure of the background noise hardly attenuates between Pf reaching the upper
surface of the vibrating membrane 113 and the sound pressure Pb reaching the lower surface of
the vibrating membrane 113. That is, with regard to background noise, the difference between
the sound pressure Pf reaching the upper surface of the vibrating membrane 113 and the sound
pressure Pb reaching the lower surface of the vibrating membrane 113 is small.
[0056]
FIG. 9 is a graph showing the relationship between the distance R from the sound source
converted to a logarithm and the sound pressure P output from the microphone converted to a
logarithm (dB: decibel). The dotted line shows the characteristics of a normal microphone unit,
and the solid line shows the characteristics of the differential microphone unit 110B according to
the present embodiment.
[0057]
As shown in FIG. 9, the sound pressure level (dB) detected and output by the differential
microphone unit 110B according to the present embodiment is greatly reduced as compared to a
normal microphone unit as the distance from the sound source increases. Show the
characteristics. That is, in the differential microphone unit 110B according to the present
embodiment, the sound pressure level decreases more significantly as the distance from the
sound source becomes larger than that of the normal microphone unit.
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[0058]
7 to 9, since the difference (Pf-Pb) in sound pressure of background noise received by diaphragm
113 is very small, the noise indicating the background noise generated by differential
microphone unit 110B The signal is very small. On the other hand, since the difference (Pf-Pb) in
sound pressure of the speech of the speaker received by the diaphragm 113 is large, the speech
signal indicating the speech generated by the differential microphone unit 110B is growing. That
is, the differential microphone unit 110B can output a speech signal mainly indicating speech.
[0059]
<Configuration of Differential Microphone Unit 110B> Next, the configuration of the differential
microphone unit 110B according to the present embodiment will be described. FIG. 10 is a front
sectional view showing a differential microphone unit 110B according to the present
embodiment, and FIG. 11 is a sectional view taken along line XI-XI in FIG.
[0060]
As shown in FIGS. 10 and 11, the differential microphone unit 110 </ b> B includes a
microphone substrate 622. The microphone substrate 622 has a first substrate opening 622A
and a second substrate opening 622B facing one surface, and the first substrate opening 622A
and the second substrate opening 622B in the diaphragm 113. It has a substrate internal passage
622C communicating with the lower space and the outside.
[0061]
The differential microphone unit 110B according to the present embodiment includes an upper
housing 612 that covers one surface of the microphone substrate 622 (the upper surface of the
microphone substrate 622). The upper housing 612 has a first housing opening 612A and a
second housing opening 612B. Then, the upper housing 612 and the microphone substrate 622
form a first space for surrounding (accommodating) the side wall portion 112A, the vibrating
film 113, and the ASIC 240.
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[0062]
That is, the differential microphone unit 110B according to the present embodiment includes the
vibration detection unit 111. The vibration detection unit 111 is disposed at a position covering
all of the first substrate opening 622A. In addition, the vibrating film 113 of the vibration
detection unit 111 is disposed at a position covering the first substrate opening 622A.
[0063]
Sound waves propagating from the outside reach the top surface of the vibrating membrane 113
through the first housing opening 612A and the first space. Also, sound waves propagating from
the outside reach the lower surface of the vibrating membrane 113 through the second housing
opening 612B and the substrate internal passage 622C.
[0064]
Further, as described above, the configuration of the vibration detection unit 111 including the
side wall portion 112A, the vibrating film 113, and the ASIC 240 is the same as that in the first
embodiment, and thus the detailed description will not be repeated here.
[0065]
Since the differential microphone unit 110B is configured as described above, the sound pressure
Pf of the sound wave incident from the first housing opening 612A is applied to the upper
surface of the diaphragm 113.
The sound pressure Pb of the sound wave incident from the first housing opening 612B is
applied to the lower surface of the vibrating membrane 113. Thus, the vibrating membrane 113
vibrates based on the difference between the sound pressure Pf and the sound pressure Pb.
[0066]
Here, in order to obtain good differential microphone characteristics, adhesion between the
03-05-2019
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microphone substrate 622 and the side wall portion 112A is important. If there is an acoustic
leak between the microphone substrate 622 and the side wall portion 112A, the sound pressure
coming from the second substrate opening 622B can not be transmitted to the diaphragm 113,
and good differential microphone characteristics can not be obtained. . In this embodiment, in the
first substrate opening 622A, all four sides of the lower surface of the side wall portion 112A
holding the vibrating film 113 are in close contact with the upper surface of the microphone
substrate 622. By taking measures against leakage, it is possible to obtain good differential
microphone characteristics without variation, and to obtain a microphone unit that is resistant to
environmental changes.
[0067]
Therefore, according to differential microphone unit 110B in the present embodiment, sound
pressure differences are input using sound waves at two points on upper housing 612, that is, at
first housing opening 612A and second housing opening 612B. Can be detected. Further, by
mounting the differential microphone unit 110B configured by one diaphragm 113 at high
density, a small and lightweight microphone unit can be realized.
[0068]
In addition, the sound wave arrival time from the first housing opening 612A to the upper
surface of the vibrating membrane 113 may be equal to the sound wave arrival time from the
second housing opening 612B to the lower surface of the vibrating membrane 113. . In order to
equalize the sound wave arrival time, for example, the path length of the sound wave from the
first housing opening 612A to the vibrating membrane 113 and the path length of the sound
wave from the second housing opening 612B to the vibrating membrane 113 are It may be
configured to be equal. The path length may be, for example, the length of a line connecting the
centers of the cross sections of the path. Preferably, the path length ratio is equal to ± 20%
(range of 80% or more and 120% or less), and the housing internal space volume on the side
communicating with the housing opening 612A across the vibrating membrane 113, and the
housing The acoustic impedance from the housing opening 612A to the vibrating membrane 113
and the housing opening by making the housing internal space volume on the side
communicating with the opening 612B equal to ± 50% (50% or more and 150% or less) Since
the acoustic impedance from 612 B to the vibrating membrane 113 can be made equal,
differential microphone characteristics can be made particularly good in a high frequency band.
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[0069]
With this configuration, the sound pressure (gain) reaching the vibrating membrane 113 from
the first housing opening 612A and the housing opening 612B, and from the first housing
opening 612A and the second housing opening 612B. The arrival time of the sound wave
reaching the vibrating membrane 113, that is, the phase can be made uniform, and a more
accurate noise removal function can be realized.
[0070]
Then, as described above, the sound pressure sharply attenuates at a position close to the sound
source (the left side of the graph in FIG. 4) and gently attenuates to a position away from the
sound source (the right side in the graph of FIG. 4).
Therefore, with regard to the sound wave corresponding to the voice uttered by the speaker, the
sound pressure Pf transmitted to the upper surface of the diaphragm 113 and the sound
pressure Pb transmitted to the lower surface of the diaphragm 113 are largely different. On the
other hand, with regard to sound waves with respect to surrounding background noise, the
difference between the sound pressure Pf transmitted to the upper surface of the vibrating
membrane 113 and the sound pressure Pb transmitted to the lower surface of the vibrating
membrane 113 becomes very small.
[0071]
Since the difference between the sound pressures Pf and Pb of the background noise received by
the diaphragm 113 is very small, the sound pressure with respect to the background noise is
substantially canceled by the diaphragm 113. On the other hand, since the difference between
the sound pressures Pf and Pb of the speech of the speaker received by the diaphragm 113 is
large, the sound pressure for the speech is not canceled by the diaphragm 113. In this manner,
the differential microphone unit 110B uses the ASIC 240 to output an audio signal obtained by
vibrating the diaphragm 113 as a transmission audio signal.
[0072]
As described above, in the present embodiment, as shown in FIG. 10, even when the side wall
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portion 112A is in contact with the inner wall surface of the upper housing 612, it is possible to
propagate the sound wave to the vibrating film 113. . That is, side wall portion 112A according
to the present embodiment propagates sound waves to diaphragm 113 while raising the strength
of differential microphone unit 110B by contacting microphone substrate 622 and the inner wall
surface of upper housing 612. It is possible.
[0073]
That is, the differential microphone unit 110B according to the present embodiment reduces the
height of at least a part of the side wall 112A in the direction of the housing opening 612A with
respect to the vibrating membrane 113. It is possible to secure the cross-sectional area of the
sound path from the case opening 612A to the vibrating membrane 113 without reducing the
strength of the sensor, and to achieve both thinning of the differential microphone unit 110B and
good acoustic characteristics. I can do it.
[0074]
In other words, the differential microphone unit 110B according to the present embodiment can
keep the resonance frequency high by shortening the sound path length.
Then, the volume of the differential microphone unit 110B can be reduced. In addition, notch
112B of sidewall 112A can be easily formed, for example, by etching or the like.
[0075]
Then, as described above, also in the differential microphone unit 110B according to the present
embodiment, as shown in FIG. 5, the hole 112D may be formed on the side of the housing
opening 611A of the side wall 112C. Thereby, the side wall opening can be easily formed.
[0076]
In the above embodiment, the microphone substrate 622 is formed by laminating a plurality of
substrates, and comprises the upper and lower substrate layers sandwiching the substrate
internal passage 622C extending in the parallel direction to the surface of the microphone
substrate 622 It is good.
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[0077]
As a material of the microphone substrate 622, for example, a glass epoxy substrate (FR4), a BT
resin substrate, a ceramic substrate, a silicon substrate, a glass substrate or the like can be used.
[0078]
In constructing the microphone unit 110B, it is required that the difference in linear expansion
coefficient between the vibrating membrane 113 and the side wall portion 112A and the upper
substrate on which the same is mounted be as small as possible. Stress due to thermal strain is
applied to the vibrating membrane 113, which causes a change in sensitivity of the microphone
and a malfunction.
[0079]
Therefore, when using the vibrating film 113 and the side wall 112A made of a silicon material,
the material of the microphone substrate 622, in particular, the upper substrate on which the
vibrating film 113 and the side wall 112A are mounted is a silicon substrate or silicon. It is
preferable to use a glass substrate or ceramic substrate having an equal linear expansion
coefficient.
[0080]
In particular, when the vibrating membrane 113 and the side wall portion 112A are flip-chip
mounted on the microphone substrate 622, the stress generated by the difference in linear
expansion coefficient directly affects the vibrating membrane 113, so the material of the
microphone substrate 622, particularly, It is preferable to use a silicon substrate or a glass
substrate or ceramic substrate having a linear expansion coefficient equal to that of silicon on the
upper substrate side on which the vibrating film 113 and the side wall portion 112A are
mounted.
[0081]
Further, when the side wall portion 112A abuts on the upper housing 612, it is required that the
difference between the linear expansion coefficients of the vibrating membrane 113 and the side
wall portion 112A and the upper housing 612 be as small as possible. When it occurs, stress due
to thermal strain is applied to the diaphragm 113, causing a change in sensitivity of the
microphone and a malfunction.
[0082]
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Therefore, when using the vibrating film 113 and the side wall portion 112A formed of a silicon
material, it is possible to use a silicon substrate or a glass substrate or ceramic substrate having a
linear expansion coefficient equal to that of silicon for the material of the upper housing 612.
preferable.
[0083]
The method of relieving stress distortion of the vibrating film 113 caused by the difference in
linear expansion coefficient by appropriately selecting the material of the microphone substrate
622 is not limited to the case where the side wall portion 112 has an opening, but also to the
side wall portion 112. It is applicable even if it is the usual composition which does not have an
opening.
[0084]
It should be understood that the embodiments disclosed herein are illustrative and nonrestrictive in every respect.
The scope of the present invention is indicated not by the above description but by the claims,
and is intended to include all modifications within the meaning and scope equivalent to the
claims.
[0085]
FIG. 1 is a block diagram showing an entire configuration of an audio signal transmitting and
receiving device according to a first embodiment.
FIG. 1 is a front cross-sectional view showing a microphone unit according to Embodiment 1;
FIG. 2A is a perspective view and a plan view of a side wall portion according to Embodiment 1;
It is front sectional drawing which shows a vibrating membrane and a side wall part.
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It is front sectional drawing which shows the modification of the side wall part which concerns
on Embodiment 1. FIG.
FIG. 7 is a block diagram showing an entire configuration of an audio signal transmitting and
receiving device according to a second embodiment.
It is front sectional drawing which shows a vibration detection part periphery.
It is a graph which shows the relationship between sound pressure P and distance R from a
sound source. It is the graph which showed the relationship between what converted distance R
from a sound source into a logarithm, and what converted the sound pressure P which a
microphone outputs into a logarithm (dB: decibel). FIG. 10 is a front cross-sectional view showing
a differential microphone unit according to Embodiment 2; It is XI-XI sectional drawing in FIG.
Explanation of sign
[0086]
100A, 100B audio signal transmitting / receiving device, 110A microphone unit, 110B
differential microphone unit, 111 vibration detection unit, 112A, 112C side wall, 112B notch,
112D hole, 113 diaphragm, 120 amplifier, 130 adder, 140 Speaker, 170 transceiver unit, 611,
612 upper case, 611A, 612A first opening, 612B second opening, 621, 622 microphone
substrate, 622A first substrate opening, 622B second substrate opening Part, 622C Board
internal passage.
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